Apparatus for grinding both fields of bifocal lenses simultaneously.



No. 880,346. PATENTED SEPT. 4,1906

- B. MAYER. APPARATUS FOR GRINDING BOTH FIELDS 0F IBIPOGAL LENSES SIMULTANEOUSLY.

APPLICATION 311.211 NOV. 18. 1905.

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BENJAMIN MAYER, OF BALTIMORE, MARYLAND. APPARATUS FOR GRINDlNG 80TH FIELDS F BIFOCAL LENSES SlMULTANEOUSLY.

Specification of Letters Patent.

Patented Sept. 4, 1906.

To all whom it mayponcern;

Be itknown that I, BENJAMIN-llrlAYER, a citizen of the United States, residing at Baltimore,,in the State of Maryland, have invented certain new and useful Im rovemente in A l) aratus for Grinding Both ields of Bifocaenses Simultaneously, of which the following is a specification. This invention relates to means for grind- !0 mg bifocal optical lenses.

One object of the invention is to provide apparatus for grinding a single piece of glass to form the two fields of e b focal lens simultaneously. l

The ingiention isillusgrat'ed in the accompan swings, in w 1ch Fi -fife 1 is a top or plan view of the grinding a paratus; Fig. 2, avertical section of the grin ing apparatus and of a glass lens in position thereon. Fig. '3 is an inverted plan view of the lens-holder and a glass lens cemented thereto. Figs. 4 and 5 are vertical sections of the grindin -disk, which differ from the one shown in l igs. 1 and 2.and from each other only in the particular shape of the two grindingdaces on the disk. Fig. 6 is a front .view of a solid or single-piece bifocal lens as made by the improved grinding ap aratus and shows the arched line which ma es the division between the two fields of the lens.

The bifocal lens ground by the a paratus herein claimed is a single piece of glhss, and the letter I; in the drawings designates the lower or near .iieldfirv the/upper pr distant field, and a the arched line over the lower field. This arched division-line is the only separation between the two fields and forms neither a crease nor a projecting ridge, and when eyeglasses ors ectacles with this style of lens are; worn t c said arched line is scarcely visible. To rind this lens, I em ploy a revoluble grinding-disk D, which has at its lower side a well-known form of socket e and is mounted on an upright shaft f. The up or surface of the disk has two distinct circu ar grinding-surfaces g and h, which are closely adjoining, one being at the center and the other concentric or surrounding it. These two grinding-surfaces differ from 50 each other-as, for instance, one may be a fiat plane and the other a convex or a concave. The smaller and central surface 9 serves to grind the lower or near ficld' of the lens, and the surrounding surface h grinds A stud or pin I is suitably secured at the center of the disk and center of the small rinding-surface and projects upward; A

ens-holder comprises a block J of suitable sha e and means for connecting the block with the said center stud, whereby the block may be retained in stationary osition while the grinding-disk revolves. Te shape and size of the block J must be such that it will properly overlap onto both of the two grindlug-surfaces g h. In the resent instance the lens-holder bluck has a role 7c of the size of or a little larger than the stud I, so that it will take over the stud, as shown, and this hole constitutes one means for connecting the lens-holder with the center stud The block J has sufficient width of face at one side of the hole It to receive the glass lens. The block has position above the rinding-disk with said hole coincident with t c axis of the disk.

The glass lens before it is ground is to be secured to the lens-holder, as usual, by cement Z.

In grinding the piece of glass 0, which is cemented to the block J, overlaps both grinding-surfaes and has a portion in contact with i one grinding-surface and a different portion in contact with the other grinding-surface at the same time. The disk with the two grindin -surfaces revolves, the lens holder is retained by connection with the center stud, and it is only necessary to keep the lens-holder from mogement while the grinding operation pro cec s.

As already ind outed, the character of the two grinding-sun aces of any one disk may be varied withoutlimit to meet the re 'uirements of the manufacturing 0 tician. 'gs. 4 and 5 show two exam lcs. tion of a form of isk where the center grindlug-surface is concave and the concentric gruuling-surface .is flat. section of a form of disk where the center grinding-surface is concave and the concenin the same relation to both surfaces ig. 4 shows the sectoo Fi 5 shows the tric grinding-surface also concave, but of a difl'crcnt degree or radius.

diately adjoinin the other and one of said surfaces adapted to grind the near field and the other adapted to rind the distance living thus described my invention, what I claim as new, and desire to secure by Letters Patent, is l 1. A revolublc grinding-disk lmving two field; a lensdlo ding bloc having a holeand 2o 5 distinct circulargrindin -surf ces-one 0011 1' adapted to overlap bothof said two grindingii i surfaces at. the same time; and means c0ncentric with respect tot e oth r; a stud pm jecting at the center; and n, lens-holder ref 'neeting with said hole to retain the lens-holdmined in place by connection will: said (-ening block in position overlapping both grindter stud and overlo )ping both ol'uiaid two ing surl'uees. 7 w x0 grimling-surfaces,,wliereby a solid or single, ln testimony whereof I allix my signature glnss may have two lenses of dill'erent foci ground simultaneously.

2. Amip mrutns l'orgrindiuglmthlieldsol' hifoeul lenses, comprising u l'evoluble disk Witnesses. 15 having two dill'erent grindingsurfuces(me l CHAS. B. MANN,

being eom'entlic with respect to und inuuc- Joux W. llEwEs.

in presence of two witnesses.

BENJAMIN MAYER. 

